Name the elements with a constant oxidation state and elements with a variable oxidation state.

Elements with a constant oxidation state include:
• chemical elements of groups IA, IIA, IIIA, having the oxidation state, respectively, + 1, + 2, + 3;
• fluorine having an oxidation state of -1;
• oxygen, exhibiting in the overwhelming majority of compounds the oxidation state -2;
• hydrogen, which has an oxidation state of +1 in compounds with most non-metals, and an oxidation state of -1 in compounds with metals.
Other chemical elements exhibit variable oxidation states.

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